Semiconductor devices are made on substrates, such as silicon substrates, glass plates or the like, often termed wafers, for use in computers, monitors, and the like. These devices are made by a sequence of fabrication steps, such as thin film deposition, oxidation, etching, polishing, and thermal and lithographic processing. Although multiple fabrication steps may be performed in a single processing apparatus, substrates typically must be transported between different processing tools for at least some of the fabrication steps.
Substrates are often stored in carriers for transfer between processing tools and other locations. In order to ensure that a processing tool does not idle, a nearly continuous supply of unprocessed substrates should be available to the tool. Thus, loading and storage apparatuses are conventionally located adjacent each processing tool. Such loading and storage apparatuses generally include one or more docking stations where substrate carriers are opened and individual substrates are extracted from the carriers and transported to a processing tool, as well as including a plurality of storage shelves positioned above the docking stations, a factory load location for receiving carriers at the loading and storage apparatus, and a robot adapted to transfer carriers among the factory load location, the docking stations and the plurality of storage shelves. The robot may include an end effector coupled to a support structure. Typically the support structure comprises a vertical guide and a horizontal guide configured so that the end effector may move horizontally and vertically among the docking stations, the plurality of storage shelves and the factory load location.
The loading and storage apparatuses may be modularly designed (e.g. having components that are mounted to a frame typically extending in front of a single processing tool) or may be nonmodular in design (e.g., having components that may be mounted independently and typically having horizontal and/or vertical guides that extend in front of a plurality of processing tools).
After a carrier is received at the factory load location, it may be moved by the robot from the factory load location to one of the storage shelves. Thereafter, the carrier may be moved from the storage shelf to a docking station. After the substrates have been extracted from the carrier, processed, and returned to the carrier, the carrier may be moved by the robot from the docking station to one of the storage shelves. Thereafter, the carrier may be moved by the robot from the storage shelf to the factory load location. Shuffling of the substrate carriers among the storage shelves, the factory load location and the docking station may place a significant burden on the robot, and may extend the period of time during which the substrates in the carrier are present in the factory without being processed. It accordingly would be desirable to streamline the handling of substrate carriers.